Integration of pressure-sensitive paint with persistent phosphor: A light-charged pressure-sensing system.

A novel pressure-sensitive paint has been developed by mixing phosphor Sr4Al14O25:Eu,Dy with pressure-sensitive luminophore PtTFPP in a polyethylene binder. The phosphor particles served as hosts for PtTFPP molecules while providing excitation light via their bright blue/green luminescence. The unique long afterglow of Sr4Al14O25:Eu,Dy allows the coating to be charged by a light source (UV-LED or even sunlight) in advance, and then the luminescent signals can be collected by using a color camera for pressure measurement (without an external light source). The persistent luminescence and the pressure-sensitive signal correspond to the green and red channels, respectively. The errors due to time-varying persistent luminescence can be removed by taking an intensity ratio between the two channels. The current formulation of this light-charged pressure-sensitive paint (LC-PSP) has been optimized for the maximum signal level. It showed similar pressure sensitivity to typical pressure-sensitive paints (PSPs), and its capability was demonstrated through a nitrogen jet impingement experiment. This light-charged PSP can be truly free of light source during measurement, which greatly simplifies the optical system and avoids errors due to the inconsistent illumination field, and thus provides a solution for PSP applications in facilities with limited optical access.